U.S. patent application number 11/231265 was filed with the patent office on 2006-05-25 for solder for fabricating solder bumps and pumping process.
Invention is credited to Yi-Hsiun Cheng, Chia-Chieh Hu.
Application Number | 20060108693 11/231265 |
Document ID | / |
Family ID | 36460198 |
Filed Date | 2006-05-25 |
United States Patent
Application |
20060108693 |
Kind Code |
A1 |
Cheng; Yi-Hsiun ; et
al. |
May 25, 2006 |
Solder for fabricating solder bumps and pumping process
Abstract
A bumping process including following steps is disclosed. First,
a wafer is provided, wherein the wafer has an active surface and
bonding pads disposed on the active surface. Next, solder material
is provided for forming solder posts on the bonding pads, wherein
the solder material for forming the solder posts includes flux,
alloy powder and organic solderability preservation material (OSP
material). The OSP material encapsulates the surfaces of the alloy
powder and is suitable for volatilizing in temperature between
210.degree. C. and 240.degree. C. Afterwards, the solder posts are
reflowed to form solder bumps, so that the OSP material
volatilizes. The solder material for fabricating solder bumps and
the bumping process are capable of reducing the voids in the solder
bumps probably produced after the solder posts are reflowed, which
benefits to enhance reliability of the solder bump and the
production yield of a bumping process.
Inventors: |
Cheng; Yi-Hsiun; (Hsinchu
City, TW) ; Hu; Chia-Chieh; (Kaohsiung City,
TW) |
Correspondence
Address: |
J C PATENTS, INC.
4 VENTURE, SUITE 250
IRVINE
CA
92618
US
|
Family ID: |
36460198 |
Appl. No.: |
11/231265 |
Filed: |
September 19, 2005 |
Current U.S.
Class: |
257/772 ;
257/E21.508; 257/E23.021 |
Current CPC
Class: |
H01L 2224/0508 20130101;
H01L 2224/1147 20130101; H01L 2224/05166 20130101; H05K 2203/122
20130101; H01L 2924/014 20130101; H01L 2924/01022 20130101; B23K
35/3612 20130101; H05K 3/282 20130101; H01L 2924/01073 20130101;
H01L 2224/05155 20130101; H01L 2924/01013 20130101; H01L 2224/05647
20130101; H01L 2224/05124 20130101; H01L 2224/05572 20130101; H01L
24/05 20130101; H01L 2224/05027 20130101; H01L 24/11 20130101; H05K
2203/043 20130101; H05K 3/3485 20200801; H01L 24/13 20130101; H01L
2924/01082 20130101; H01L 2924/01047 20130101; H01L 2924/01033
20130101; B23K 35/0244 20130101; H01L 2224/05001 20130101; H01L
2224/131 20130101; H01L 2924/01006 20130101; H01L 2224/29111
20130101; H01L 2924/01029 20130101; H01L 2224/05022 20130101; H01L
2924/00013 20130101; H01L 2924/01023 20130101; H01L 2224/05181
20130101; H01L 2224/29111 20130101; H01L 2924/01029 20130101; H01L
2224/29111 20130101; H01L 2924/01047 20130101; H01L 2224/131
20130101; H01L 2924/014 20130101; H01L 2924/00013 20130101; H01L
2224/13099 20130101; H01L 2224/05647 20130101; H01L 2924/00014
20130101; H01L 2224/05124 20130101; H01L 2924/00014 20130101; H01L
2224/05155 20130101; H01L 2924/00014 20130101; H01L 2224/05166
20130101; H01L 2924/00014 20130101; H01L 2224/05181 20130101; H01L
2924/00014 20130101 |
Class at
Publication: |
257/772 |
International
Class: |
H01L 23/48 20060101
H01L023/48 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2004 |
TW |
93128686 |
Claims
1. A solder material for fabricating solder bumps, mainly
comprising: flux; alloy powder; and organic solderability
preservation material (OSP material), used for encapsulating the
alloy powder.
2. The solder material for fabricating solder bumps as recited in
claim 1, wherein the material of the alloy powder comprises
lead-contained alloy or lead-free alloy.
3. The solder material for fabricating solder bumps as recited in
claim 1, wherein the material of the alloy powder comprises
tin-lead alloy or tin-silver-copper alloy.
4. The solder material for fabricating solder bumps as recited in
claim 1, wherein the chemical formula (1) of the OSP material is:
##STR3## wherein, R comprises aryl or alkyl: C0.about.C7 and X
comprises hydrogen (H), chlorine (Cl) or nitrogen dioxide
(NO.sub.2).
5. The solder material for fabricating solder bumps as recited in
claim 1, wherein the OSP material is suitable for volatilizing in
temperature between 210.degree. C. and 240.degree. C.
6. A bumping process, comprising: providing a wafer having an
active surface and a plurality of bonding pads disposed on the
active surface; providing a solder material for forming a plurality
of solder posts on the bonding pads wherein the solder material
comprises flux, alloy powder and organic solderability preservation
material (OSP material) for encapsulating the alloy powder; and
reflowing the solder posts for volatilizing the OSP material to
form a plurality of solder bumps.
7. The bumping process as recited in claim 6, wherein the method
for forming the solder posts comprises: providing a mask layer
having a plurality of openings on the wafer, wherein the openings
of the mask layer are used for exposing the bonding pads; filling
the solder material into the openings for forming the solder posts;
and removing the mask layer.
8. The bumping process as recited in claim 6, wherein the mask
layer comprises a stencil or a patterned photosensitive film.
9. The bumping process as recited in claim 6, further comprising
forming an under bump metallurgy layer on each of the bonding pads
respectively before forming the solder posts.
10. The bumping process as recited in claim 6, wherein the OSP
material is suitable for volatilizing in temperature between
210.degree. C. and 240.degree. C.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of Taiwan
application serial no. 93128686, filed on Sep. 22, 2004. All
disclosure of the Taiwan application is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of Invention
[0003] The present invention relates to solder material and a
semiconductor manufacturing process, and particularly to solder
material for fabricating solder bumps and a bumping process.
[0004] 2. Description of the Related Art
[0005] As a widely used chip packaging technology, a flip-chip
bonding technology (F/C bonding technology) can be briefly
described as follows. A chip with a plurality of bonding pads
arranged in area array on an active surface thereof is provided
first. A plurality of solder bumps are then formed on the bonding
pads of the chip. Afterwards, the chip is flipped such that the
solder bumps formed on the chip are electrically and mechanically
connected to a plurality of bump pads on a substrate or a PCB
(printed circuit board). The F/C bonding technology is overwhelming
in chip packages with high pin count, since it has a downsized
packaging area and considerably short transmission paths. Today,
the F/C bonding technology has been adopted in many applications
already.
[0006] In order to bond a chip on the surface of the substrate or
PCB through F/C bonding technology according to the prior art, a
bumping process is performed first to form a plurality of solder
bumps on an active surface of a chip. Generally, the bumping
process may be performed by following steps, for example. First, a
layer of stencil or a photosensitive film having a plurality of
openings and used as a mask layer is formed on an active surface of
a chip or a wafer in advance, wherein the bonding pads are exposed
by the corresponded openings. Then, solder material is filled into
the openings by printing, so that a plurality of solder posts are
formed on the bonding pads. Thereafter, the above-described stencil
or photosensitive film is removed such that the solder posts on the
bonding pads are exposed. Finally, the solder posts are reflowed
and cooled down to form a plurality of spherical solder bumps on
the corresponded bonding pads.
[0007] The above-mentioned solder material for fabricating solder
bumps is generally made of alloy powder as the major composition
thereof. During reflowing, the alloy powder likely causes oxidation
reaction and produces unwanted oxides and impurities. To remove the
unwanted oxides and impurities, flux is often added in the solder
material. However, the added flux may react with the oxides in the
solder material or a polymer layer formed on the substrate and
produce gas during refolwing. The gas such as vapor, the carbon
dioxide (CO.sub.2) or the like would form voids in the solder bumps
after reflowing. Usually, flux with stronger deoxidizing capability
is used to reduce oxidation of the alloy powder. The flux with
stronger deoxidizing capability has a relatively high acidity, so
that the residual flux after forming the spherical solder bumps may
harm the solder bumps. As described above, reliability and
production yield of solder bumps are affected by the voids formed
in the solder bumps and the flux with stronger deoxidizing
capability and high acidity.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to provide solder material
for fabricating solder bumps with high reliability. The solder
material is capable of reducing oxidation of the alloy powder
thereof and reducing usage amount of the flux effectively.
[0009] The present invention is directed to provide a bumping
process with a higher production yield. During the bumping process,
solder bumps are formed by the solder material provided by the
present invention, so that the voids generated during reflowing are
significantly reduced.
[0010] As embodied and broadly described herein, the present
invention provides a solder material for fabricating solder bumps.
The solder material includes flux, alloy powder and organic
solderability preservation material (OSP material), wherein the OSP
material encapsulates the alloy powder and the OSP material is
suitable for volatilizing in temperature between 210.degree. C. and
240.degree. C.
[0011] In an embodiment of the present invention, the material of
the above-mentioned alloy powder includes lead-contained alloy or
lead-free alloy, for example, tin-lead alloy or tin-silver-copper
alloy. In addition, the OSP material can be expressed by the
following chemical formula (1): ##STR1##
[0012] Wherein, R represents aryl or alkyl: C0.about.C7 and X
represents, for example, hydrogen (H), chlorine (Cl) or nitrogen
dioxide (NO.sub.2), for example.
[0013] As embodied and broadly described herein, the present
invention further provides a bumping process including following
steps. First, a wafer is provided, wherein the wafer has an active
surface and a plurality of bonding pads disposed on the active
surface. Next, solder material is provided for forming a plurality
of solder posts on the bonding pads, wherein the solder material
for forming the solder posts includes flux, alloy powder and
organic solderability preservation material (OSP material). The OSP
material encapsulates the surfaces of the alloy powder and is
suitable for volatilizing in temperature between 210.degree. C. and
240.degree. C. Afterwards, the solder posts are reflowed to formed
a plurality of solder bumps, so that the OSP material
volatilizes.
[0014] In a preferable embodiment of the present invention, the
method for forming solder posts can be described as follows. First,
a mask layer having a plurality of openings is formed on a wafer,
wherein the openings of the mask layer are used for exposing the
bonding pads. Next, the solder material is filled into the openings
for forming solder posts. Afterward, the mask layer is removed. The
above-mentioned mask layer is, for example, a stencil or a
patterned photosensitive film. Further, prior to forming the solder
posts, for example, an under bump metallurgy layer is formed on
each bonding pad, respectively.
[0015] In the solder material of the present invention, the
surfaces of the alloy powder is encapsulated by the organic
solderability preservation material (OSP material), such that the
alloy powder is isolated from the atmosphere and the alloy powder
is prevented from oxidation substantially. The OSP material would
volatilize after a high-temperature process (reflowing) without
being remained in the solder. By utilizing the OCP material, the
usage amount of the flux is effectively reduced, the voids
generated inside the solder bumps probably produced after reflowing
can be significantly decreased. In addition, the OCP material can
work with flux having low acidity to enhance reliability of the
solder bump and the production yield of the bumping process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments of the invention and, together with the description,
serve for explaining the principles of the invention.
[0017] FIG. 1A.about.FIG. 1F are diagrams showing the sequent steps
of a bumping process of the present invention.
DESCRIPTION OF THE EMBODIMENTS
[0018] FIG. 1A.about.FIG. 1F are diagrams showing the sequent steps
of a bumping process of the present invention.
[0019] Referring to FIG. 1A, a wafer 100 is provided first. The
wafer 100 has an active surface 100a, on which a plurality of
bonding pads 102 (only one is shown in the FIG. 1A) and a
passivation layer 104 are disposed. The passivation layer 104
covers the active surface 100a of the wafer 100 and the bonding
pads 102 are exposed by the openings 104a of the passivation layer
104. In an embodiment, the material of the bonding pads 102 is, for
example, aluminum (Al) or copper (Cu), while the material of the
passivation layer 104 is, for example, silicon nitride (SiNx) or
the like.
[0020] Next referring to FIG. 1B, an under bump metallurgy layer
106 is formed on each bonding pad 102, respectively. The under bump
metallurgy layer 106 includes, for example, an adhesion layer 106a,
a barrier layer 106b and a wetting layer 106c. As shown in FIG. 1B,
the adhesion layer 106a is disposed on the surface of the bonding
pad 102 and made of, for example, titanium (Ti), aluminum (Al) or
tantalum (Ta). The barrier layer 106b is disposed on the adhesion
layer 106a and made of, for example, nickel-vanadium alloy. The
wetting layer 106c is disposed on the barrier layer 106b and made
of, for example, copper. The method for forming the above-described
adhesion layer 106a, barrier layer 106b and wetting layer 106c is,
for example, sputtering or evaporation. In a preferrable
embodiment, while the bonding pad 102 is made of aluminum, the
stacking structure of the under bump metallurgy layer 106
containing an adhesion layer 106a, a barrier layer 106b and a
wetting layer 106c is preferably composite by, for example,
aluminum/nickel-vanadium alloy/copper (Al/NiV/Cu). While the
bonding pad 102 is made of copper, the stacking structure of the
under bump metallurgy layer 106 containing an adhesion layer 106a,
a barrier layer 106b and a wetting layer 106c is preferably
composite by, for example, titanium/nickel-vanadium alloy/copper
(Ti/NiV/Cu).
[0021] Referring to FIG. 1C, a mask layer 110 is formed on the
wafer 100, wherein the mask layer 110 has a plurality of openings
110a (only one is shown in FIG. 1C) used for exposing the under
bump metallurgy layer 106 on the bonding pad 102. In an embodiment,
the mask layer 110 is a stencil and made of metal, for example. In
another embodiment, the mask layer 110 can be a patterned
photosensitive film made of, for example photoresist material. The
mask layer 110 is formed by entirely coating a photoresist material
layer (not shown in the figure) on the wafer 100 and patterning the
photoresist material layer by photolithography and developing
process.
[0022] Further referring to FIG. 1D, the solder material is filled
into the openings 110a of the mask layer 110 for forming solder
posts 112 by printing or other process. Remarkably, the solder
material used in the present invention includes flux, alloy powder
and organic solderability preservation material (OSP material). The
material of the alloy powder is, for example, lead-contained
tin-lead alloy or lead-free tin-silver-copper alloy. In addition,
the OSP material encapsulates the surfaces of the alloy powder for
isolating the alloy powder from the atmosphere. In an embodiment,
the OSP material can be expressed by the following chemical formula
(1): ##STR2## Where, R represents, for example, aryl or alkyl:
C0.about.C7, X represents, for example, hydrogen (H), chlorine (Cl)
or nitrogen dioxide (NO.sub.2) and the OSP material is suitable for
volatilizing in temperature between 210.degree. C. and 240.degree.
C.
[0023] Further referring to FIG. 1E, the mask layer 110 is then
removed. If the mask layer 110 is a stencil, the mask layer 110 can
be directly removed from the wafer 100; if the mask layer 110 is a
photosensitive film, the mask layer 110 can be removed by using
etchant or the like.
[0024] Furthermore referring to FIG. 1F, a reflowing process is
performed. Since the processing temperature during the reflowing
process is higher than the volatilizing temperature range between
210.degree. C. and 240.degree. C., therefore the OSP material would
be volatilized during the reflowing process and the solder posts
112 is reflowed to form spherical solder bumps 114.
[0025] Remarkably, the processing sequence in the other embodiments
of the present invention can be optionally altered this way, that
is a reflowing process is performed to primarily form spherical
solder bumps 114 first, followed by removing the mask layer 110.
Besides, after removing the mask layer 110, another process of
reflowing the solder bumps can be further performed to strengthen
the mechanical strength of the solder bump 114.
[0026] From the above described, it can be seen that the solder
alloy powder of the present invention are encapsulated by organic
solderability preservation material (OSP material) to insulate the
alloy powder from the atmosphere for avoiding oxidation
substantially. After the reflowing, the OSP material is not
residual in the solder bumps since the OSP material is volatilized
at a high-temperature. In this way, not only the usage amount of
the flux in the solder material is effectively reduced, but also
the voids generated in the solder bumps probably produced after the
reflowing is decreased. Besides, since the alloy powder gets a
pretty good anti-oxidation protection in the present invention, the
restricted oxygen-content in a reflowing oven allows to be
relatively increased, which leads to reduce the nitrogen gas usage
and save the production cost. In other words, the solder material
for fabricating solder bumps and the bumping process benefit to
enhance reliability of the solder bump and the production yield and
save the production cost.
[0027] The foregoing description of the preferred embodiment of the
present invention has been presented for purposes of illustration
and description. It is not intended to be exhaustive or to limit
the invention to the precise form or to exemplary embodiments
disclosed. Accordingly, the foregoing description should be
regarded as illustrative rather than restrictive. Obviously, many
modifications and variations will be apparent to practitioners
skilled in this art. The embodiments are chosen and described in
order to best explain the principles of the invention and its best
mode practical application, thereby to enable persons skilled in
the art to understand the invention for various embodiments and
with various modifications as are suited to the particular use or
implementation contemplated. It is intended that the scope of the
invention be defined by the claims appended hereto and their
equivalents in which all terms are meant in their broadest
reasonable sense unless otherwise indicated. It should be
appreciated that variations may be made in the embodiments
described by persons skilled in the art without departing from the
scope of the present invention as defined by the following claims.
Moreover, no element and component in the present disclosure is
intended to be dedicated to the public regardless of whether the
element or component is explicitly recited in the following
claims.
* * * * *